Buckstay connection for furnace walls



April 23, 1968 G. J. STALPH 3,379,177

BUCKSTAY CONNECTION FOR FURNACE WALLS 4 Sheets-Sheet 1 Filed Dec. 29. 1966 INVENTOR. GUNT'EE J- 57A LPH ATTORNEY April 23, 1968 G. J. STALPH 3,379,177

BUCKSTAY CONNECTION FOR FURNACE WALLS Filed Dec. 29. 1966 4 Sheets-Sheet 2 I m 1 4 4 I 76 & 76

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G- J. STALPH BUCKSTAY CONNECTION FOR FURNACE WALLS 4 Sheets-Sheet 5 Iczsi INVENTOR. GUNTEE J. STA/.PH

QMWJM A-rTozNEY April 23, 1968 G. J. STALPH 3,379,177

BUCKSTAY CONNECTION FOR FURNACE WALLS Filed Dec. 29. 1966 4 SheetsSheet 4 INVENTOR. GUNTEE J. S 741. PH

A T TOQNE Y United States Patent 9 3,379,177 BUCKSTAY CONNECTION FOR FURNACE WALLS Gunter J. Stalph, Windsor, Conn., assiguor to Combustion Engineering, Inc., Windsor, Conn, a corporation of Delaware Filed Dec. 29, 1966, Ser. No. 605,857 12 Claims. (Cl. 122-6) ABSTRACT OF THE DISCLGSURE Apparatus for connecting heavy buckstays about the walls of a vapor generator furnace in a manner that permits the buckstays to be attached independently of the heat exchange tubes that line the furnace walls. The buckstays are attached to vertical beams that are suspended from building steel or are bottom supported and that surround the furnace. They are connected at the ends such that the buckstays on opposed Walls serve as ties for those on adjacent walls. In order that the buckstays can undergo movement coincident with expansion and contraction of the walls they are interconnected at their ends by stifi pivotable linkage connections. The position of the links determines the position of the buckstays and the former are driven in response to signals emitted by sensors adatped to determine the position of the furnace walls relative to the buckstays.

Background of the invention This invention relates generally to high capacity vapor generators and has particular relation to improved buckstay means for contracting the walls of such vapor generators.

As a result of the ever increasing capacity and size of vapor generators, the buckstays and the vertically extending support members which provide necessary stiffening for the furnace walls have become excessively heavy. Heretofore it had been the practice to support this structure directly from the furnace and gas pass wall itself and more particularly from the heat exchanger tubes that line these Walls. Because of the great Weight of the support structure in large units this form of support was accompanied by several manifest disadvantages including a requirement that the wall thickness of the heat exchange tubes lining the furnace and gas pass Walls be increased to carry this additional load. In U.S. patent application Ser. No. 514,780 to Svendsen et al. filed Dec. 20, 1965, it has been proposed to alleviate the problem by providing vertically extending support members at the outer region of the furnace which are supported independently of the furnace walls. The buckstays that provide lateral restraint for the furnace Walls are supported from these vertical support members and tied together by means of conduits that conduct fluid from the fluid circuit of the vapor generator such that the buckstay ties will thermally expand and contract with the walls of the furnace. While such an arrangement constitutes a definite improvement over prior art structures it is undesirable to employ fluid conduits conducting high pressure and temperature fluid as tie members. The present invention therefore is directed toward a buckstay arrangement having the same advantageous features of this arrangement yet avoids the use of pressure parts as tie members.

Summary By means of the invention the ends of buckstays on adjacent walls are connected together by a stiff, pin connected link that is operated by an electric motor through a lever. The motor is, in turn, operated by sensors that are adapted to complete the motor circuit when the position of the wall relative to the buckstay through expansion 3,379,177 Patented Apr. 23, 1968 or contraction of the former is such as to require repositioning of the buckstays. The invention thus avoids the use of pressure parts for positioning the buckstays in the arrangement disclosed in U.S. application Ser. No. 514,780. It further permits each pair of buckstays to serve as tie members for each other pair of buckstays in each elevation thereby causing the expansive stresses imposed by the walls to impart a tensile loading to the buckstays which opposes its normal compression loading and thus reduces the size of the buckstays required to sustain the loads imposed.

Content of drawings FIGURE 1 is a vertical sectional view of a high capacity vapor generator employing the present invention;

FIGURE 2 is a plan section of the vapor generator taken along line 2-2 of FIGURE 1;

FIGURE 3 is a partial plan view illustrating in greater detail a typical buckstay connection;

FIGURE 4 is a sectional View taken along line 44 of FIGURE 3;

FIGURE 5 is a sectional view taken along line 55 of FIGURE 3; and

FIGURE 6 is an elevational view partly in section taken along line 6-6 of FIGURE 3.

Description of the preferred embodiment There is shown in the drawings a high capacity vapor generator 10 of the once-through type that is capable of producing vapor at pressures as high as 3500 p.s.i. and temperatures upwards of ll0O F. The vapor generator 10 includes a vertically elongated furnace 12 into which fuel and air are introduced through burners 14. The fuel is consumed within the furnace and the combustion gases pass upwardly therethrough, out the lateral outlet at the upper end thereof and then through a horizontal gas pass 16 and vertical gas pass 18. Thereafter the gases traverse an air heater (not shown) and are finally conveyed to a stack.

The vapor generator 10 includes a fluid circuit through which vaporizable fluid is forced by means of a feed pump. The fluid circuit includes an economizer 20 located in the vertical gas pass 18 which receives liquid from the feed pump. From the economizer 20 the liquid is passed to heat exchange tubes 22 that line the walls of the unit and that emanate from lower headers such as those indicated as 24-. The tubes 22 are connected at their upper ends to headers 26 which serve as collection manifolds for vapor produced in the tubes. From the headers 26 the vapor passes to superheater tube surface indicated as 28 where it is heated to its final desired temperature and from whence it is conveyed to a suitable point of use such as a turbine. Reheater tube surface, indicated as 30, may be contained within the gas pass when the vapor generator is adapted for use in a reheat power cycle.

The furnace 12 of the vapor generator 10 is rectangular in section and having pairs of opposed walls, one pair including walls 32 and 34 and the other including walls 36 and 38. The inner surface of these walls is lined with the heat exchange tubes 22 which are parallelly arranged and may be disposed on tangent spacing or provided with laterally extending fins welded together to produce a gastight surface. Outwardly of, and in engagement with, the tubes 22 is a layer of thermal insulation 40' that is supported from the tubes in known fashion. Also supported by the tubes are horizontally extending stiffener members 42 in the form of channels or I-beams. These stiffener members 42 are connected with, and supported by, the tubes 22 in a manner which permits limited lateral movement therebetween to accommodate differential expansion and contratcion of the furnace walls. Such a support arrangement is well known in the art. The vapor generator a is suspended at its upper end from building steel indicated as 44, the furnace walls being hung by means of hanger rods 46 which extend down from the building steel and connect with the upper headers 26.

In order to prevent excessive deflection of the walls of the furnace 10 incident to sudden increases in pressure within the furnace, commonly known as puffs, there is provided a heavy steel cage about the furnace including a heavy buckstay system. This cage is comprised of vertically extending steel I-beam 48 positioned at spaced horizontal intervals about the furnace. These vertically tending panels are not supported from the furnace walls but are supported independently thereof with each beam being hung from the building steel 44 through a separate support rod 50. The beams 48 that extend down along the walls of the furnace are in sliding engagement with the stiffener members 42 and the support rod 50 is so connected that the vertical beams are moved laterally as is necessary to accommodate the expansion and contraction of the furnace incident to the temperature changes that occur therein. At vertically spaced locations there is provided a buckstay system which extends about the furnace 10 with this system including buckstay trusses 52 and 54 which extend transversely of the walls 32 and 34 and buckstay trusses 56 and 58 which extend transversely of the walls 36 and 38. The buckstay trusses 52 and 54 comprise outer and inner chords, 60 and 62 respectively, connected by a number of web members 64. As shown, the endposts 66 of the trusses extend from the outer chords 60 diagonally beyond the inner chords 62 for connection to positioning apparatus hereinafter described. The buckstay trusses 56 and 58 are constructed in conventional manner with outer and inner chords, 68 and 70 respectively, and interconnecting web members 72 and endposts 74. Each of the buckstay trusses extend along the outer sides of the vertical beams 48 and have their inner chords 62 and 7 0 secured to these beams as by welding.

In order for this structural cage, comprising the vertical beams 48 and the buckstays 52 through 58, to prevent deflection of the furnace walls the extremities of the buckstays at each elevation are interconnected. It will be appreciated that the furnace will expand and contract considerably between its cold and hot conditions and the means by which the opposed buckstays at each elevation are interconnected must be such as to permit movement of these buckstays generally in accordance with the expansion and contraction of the furnace.

According to the invention, this interconnection is accomplished by means of positioning apparatus, indicated generally as 76, located at each corner of the furnace on each buckstay elevation. As shown best in FIGURE 3 the positioning apparatus comprises a connecting link 78 formed of a pair of spaced channels 80 that are pin connected at one end, indicated as 82, to the end of the inner chord 70 of buckstay 54. The link 78 is also pin connected intermediate its length at 84, to a gusset 86 connected to the inner end of endpost 66 of buckstay 52. At their outer ends the channels 80 form a lever arm pin connected to an expansion collar 90 of the positioner 76 for the purpose of positioning the link 78.

The positioner 76 includes a reversible electric motor 92 that is mounted on a platform 94, by the latter being cantilever supported from the endpost 74 of buckstay 54 by a channel 96 that is slidingly borne by a gusset 98 attached to the endpost. The motor 92 drives a shaft 100 rotatably supported in bearings attached to the platform 94. The shaft 100 is threaded at both ends and receives internally threaded collars 90, the one connected to the link 78 and the other pin connected to the outer chord 68 of buckstay 54. The arrangement is such that rotation of the shaft 100 in one direction causes the collars 90 to be moved further apart to displace the lever and thereby the link 78 in one direction while rotation of the shaft in the other direction moves the collars closer together to thus move the lever and link in the other direction.

The electric circuits to the motor 92 is closed in response to the position of the adjacent furnace wall relative to the buckstay. This is accomplished in the disclosed arrangement by means of sensors 102 and 104 (FIGURE 4) that are mounted upon the inner chord 62 of buckstay 52. The sensors 102 and 104 comprise a simple linkage comprising a pivotally mounted bar 108 and a connecting rod 110 attached at one end to the bar 108 and at the other end slidingly connected in a slotted connector 112 that is attached to the furnace wall. Mercury switches 106 attached to the bars 108 are operatively connected through electric leads to motor 92. The arrangement shown is such that the sensor 102 is adapted to operate the associated motor 92 during expansive movement of the adjacent furnace wall and sensor 104 is adapted to operate the motor 92 during contractive movement thereof.

In the operation of the hcreindescribed vapor generator 10 it will be appreciated that feedwater passed through the tubes 22 that line the walls of the unit is heated by combustion gases generated in the furnace 12 from fuel admitted through burners 14. As the temperature within the vapor generator changes in response to various load conditions placed upon the unit, the furnace walls, 32 through 38, thereof are caused to expand and contract both vertically and laterally incident to the thermally induced expansion and contraction of the pressure parts that comprise the unit. At all times the walls, which have a tendency to assume a cylindrical configuration due to the pressure within the furnace 12, are prevented from deflecting by the cage construction comprising the vertical beams 48 and buckstay trusses, 52 through 58, that surround the unit. Vertical expansion and contraction of the walls is permitted by the sliding contact that exists between the stitfeners 42 and the vertical beams 48. Lateral displacement of the walls is accommodated through the action of the positioners 76.

When, for example, additional heat is applied to the furnace and the walls thereof are caused to expand laterally outwardly, this expansion of the wall relative to its adjacent buckstay will effect a pivoted movement of the bar 108 of sensor 102 to the position shown dotted in FIGURE 4 thereby actuating the mercury switch 106 to operate the motor 92. The motor 92 operates to expand the collars 90 and thereby operate the link 78 to move the ends of the connected buckstays 52 and 56 outwardly. Since expansion in the furnace 12 is generally uniform the ends of all of the buckstays will be caused to move a substantially uniform incremental distance. When the buckstay has moved a predetermined distance of say inch the bar 108 of sensor 102 will be pivoted back to its original position to deactuate the motor 92 until such time that further expansion of the wall again actuates the switch 106 of sensor 102 to move the buckstay another incremental distance.

During expansion of the furnace walls the switches 106 associated with sensors 104 will assume the position shown dotted at the left in FIGURE 4 and therefore will remain deactuated. When, however, the temperature within the furnace decreases and the Walls contract the bar 108 will be pivoted to the position shown dotted at the right thereby closing the switch 106 to operate the motor 92 in the reverse direction. This causes the collars 90 to be moved closer together and thus alters the position of the link 78 and thereby causes the buckstays to be moved inwardly a similar incremental distance until the relative position between the wall and the buckstay is such as to pivot the bar 108 to deactuate the switch 106.

It will be appreciated that with the construction and organization of this invention a rugged cage is provided about the furnace of the vapor generator with the furnace moving up and down within this cage as a result of thermal expansion and contraction and with the cage laterally expanding and contracting in a manner generally similar to that of the furnace. The invention is useful in that lateral displacement of the cage can be etfected by means other than hot fluid conducting ties thereby removing the dunger that accompanies such a construction.

The invention is of particular advantage in that, in addition to removing the great weight of the buckstay system from the furnace walls, the weight of the buckstay system can be reduced by the requirement of smaller chord members due to the fact that the trusses in serving as ties and thus being subjected to tensile forces serve to partially offset the compression loading that normally exists in these members such that members of lesser dimensions are required to carry the loading.

It will be understood that various changes in the details, materials and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. In a vapor generator, an elongated furnace having rectangularly disposed walls lined with heat exchange tubes, means forming buckstays extending transversely of said furnace walls, and means interconnecting the ends of said buckstays including:

means forming links pin-connected between the ends of adjacent buckstays;

means for restraining movement in said link means against displacement-inducing forces against said buckstays, and means for altering the position of said link means and thereby the position of said buckstays in response to a predetermined lateral displacement of said furnace walls.

2. The organization of claim 1 wherein the means for altering the position of said link means includes:

motor means operatively connected to said link means for altering the position thereof, and

means for sensing displacement of said furnace walls operatively connected to said motor means for driving the same to alter the position of said link means upon the occurrance of a predetermined sensed displacement.

3. The organization of claim 2 including:

reversible electric motor means operatively connected to said link means for altering the position thereof, and

sensing 'means operatively connected to said motor means comprising normally open switch means that are closed upon the occurrence of a predetermined displacement of said furnace walls.

4. The organization of claim 3 wherein said sensing means includes:

a pivotable bar mounted to one of said buckstays,

a connecting rod attached between said pivotable bar and said one furnace wall and adapted to pivot said bar upon displacement of said one furnace wall relative to said one buckstay, and

a mercury switch attached to said pivotable bar and adapted to close an electric circuit to said motor means upon undergoing a predetermined amount of pivotal movement.

5. The organization of claim 4 including:

first sensing means for operating said motor means during expansive displacement of said furnace walls, and

second sensing means for operating said motor means during contractive displacement of said furnace walls.

6. The organization of claim 1 wherein said link means comprises:

an elongated rigid structural member pin-connected at one of its ends to the end of one buckstay and pinconnected intermediate its length to the end of an adjacent buckstay,

said structural member including a lever arm connected to means for altering the position thereof in response to :a predetermined lateral displacement of said furnace walls.

7. The organization of claim 6 wherein said means for altering the position of said link means comprises:

means forming an expandable and contractable shaft connected between the end of said lever arm and said one buckstay, and

reversible motor means operatively connected to said shaft for operating the same in one direction upon lateral displacement of said furnace walls in one direction and for operating the same in the other direction upon lateral displacement of said furnace walls in the other direction.

8. The organization of claim 7 including:

a rotatable shaft having threaded ends;

expansion collars mounted to said ends, one of said expansion collars being pin-connected to the end of said lever arm and the other being pin-connected to said one buckstay;

reversible electric motor means operatively connected to said shaft for rotating the same upon excitation of said motor;

means for operating said motor means comprising sensing means for determining the position of said furnace walls relative to said buckstays and for actuating said motor in an appropriate direction upon a predetermined relative displacement of said furnace walls.

9. The organization of claim 8 means includes a pivotable bar mounted to one of said buckstays,

a connecting rod attached between said pivotable bar and said one furnace wall and adapted to pivot said bar upon displacement of said one furnace wall relative to said one buckstay,

and a mercury switch attached to said pivo'table bar and adapted to close an electric circuit to said motor means upon undergoing a predetermined amount of pivotal movement.

10. The organization of claim 9 including first sensing means for operating said motor means during expansive displacement of said furnace walls,

and second sensing means for operating said motor means during contractive displacement of said furnace walls.

11. The organization of claim 6 including means supporting said buckstays independently of said furnace walls.

12. The organization of claim 11 wherein the support for said buckstays comprises vertical beams engaging said furnace walls, said beams being disposed about the furmace and mounted with respect to said furnace in a manner that permits limited lateral movement to accommodate displacement of the walls of said furnace.

wherein said sensing References Cited UNITED STATES PATENTS 3,007,455 11/1961 Lieb et .al. 122-6 3,203,376 8/1965 Engelhardt l226 XR 3,277,870 10/1966 Reale 1226 KENNETH W. SPRAGUE, Primary Examiner. 

